1. Field of the Invention
This invention relates to a new and improved means and method of recovering fuel vapor in a fuel dispensing nozzle.
2. Background
Ever since the harmful environmental effects of gasoline vapor have been known, devices have been developed to reduce fuel vapors escaping into the atmosphere. A great amount of fuel vapors are released into the atmosphere when gasoline is pumped into an automobile from an underground storage tank at a service station. Such vapors escape into the atmosphere as gasoline is discharged from the spout of the nozzle. On a world-wide scale, millions of pounds of hazardous fuel vapors escape into the atmosphere each year from this single source. The danger of these pollutants is considered serious. Environmental Protection Agency inspectors levy large fines to service station owners who do not have or do not properly maintain vapor recovery systems.
Vapor recovery systems were first introduced in 1974. The systems are intended to recover escaping fuel vapors comprising hydrocarbons and other volatile organic compounds. While improvements over the years has been significant, excessive equipment malfunctions and user dissatisfaction persist. In particular, the present problems associated with vapor recovery systems include difficulty in handling the systems, loss in effectiveness from cuts in the rubber or plastic bellow used to cover the spout of the nozzle and filler neck of the automobile gas tank, and frequent and costly maintenance.
Presently, the two major vapor recovery systems in use are the balanced system and the vacuum assist system. The balanced system is more popular because it is less expensive and more easily maintained by the automobile service station owner. However, in the balanced system it is more difficult for the average user to handle the nozzle to maintain the proper seal between the nozzle and the filler neck.
The balanced system comprises a bellow having crimped edges which essentially extends from a fender guard the length of the nozzle spout. The combination of the pleats of the bellow and a spring-contained therein permit it to compress as the spout is inserted into the filler neck of the automobile tank. The substantially cone-shaped bellow engages and encapsulates the automobile tank filler neck forming a seal to prevent vapor from escaping during pumping. The system uses the positive pressure generated in the automobile fuel tank by the incoming fuel to force the vapor back toward the nozzle where the vapor is returned to the service station storage tank.
Besides the cuts and kinks common to systems using bellows, the balanced system is also ineffective. Motorists do not take the necessary time to make certain that the bellow forms a proper seal over the mouth of the filler neck. Some do not understand the purpose of the bellow, while others cannot position the bellow properly. The rubber or hard plastic bellow is highly resilient for durability reasons which resist the motorist's attempts to keep the spout in the filler neck. Motorists also become tired from holding the nozzle tightly against the filler neck. Often, they relax, which results in premature shut-off due to the loss of the proper seal.
The vacuum assist system uses a vacuum generating device located in the dispenser or storage tank which aspirates vapor in the automobile fuel tank. Sometimes a bellow is also secured to the nozzle, but it is not as essential as in the balance system. The vacuum assist system relies primarily on the vacuum to suck the vapor back through the nozzle. One of such arrangements is described in U.S. Pat. No. 3,826,291 which employs a positive displacement vacuum pump, installed in a dispenser area. The pump's initial high cost and the inherent high wear and maintenance cost make it an unattractive choice for service station owners.
If the vacuum assist system is used in conjunction with bellows, the bellows have the same problems mentioned above. In addition, the vacuum assist system has some of its own problems. For example, when the vacuum generating mechanism for several pumps is located in a common storage tank, the number of pumps in use has an impact on the amount of suction generated. If one pump is in use, the vacuum may be too strong which results in the recirculation of fuel or suction of additional air which results in vapor growth. If the fuel is recirculated, the motorist may be charged for gasoline already dispensed and registered on the totalizer.
On the other hand, if all the station pumps are used at the same time, there may be too little suction. This allows too much of the vapor to escape into the atmosphere making the system ineffective. Additionally, suction may be reduced to unacceptable levels if the flexible hose is too long.
Finally, overall maintenance of the vacuum assist system is very expensive. Repairs in a pump or storage tank causes serious delays and substantial financial hardships. The cost of installation is also significant.